Corrosion-resistant oil-resistant corrugated pipe inner layer coating and preparation method thereof

Abstract

The invention discloses an anti-corrosion oil-resistant corrugated pipe inner layer coating and a preparation method thereof. The coating comprises acrylic acid modified epoxy resin, epoxy phosphate, an auxiliary agent, a curing agent and water. The preparation method comprises the steps of synthesis of acrylic acid modified epoxy resin, synthesis of epoxy phosphate, epoxy mixing reaction, neutralization reaction, coating preparation and the like. The preparation method comprises the following steps: adding a copolymer side chain with acrylic acid, styrene and vinyl siloxane to a side chain in epoxy resin to obtain acrylic acid modified epoxy resin, and introducing a phosphate end group to an end group of the epoxy resin to obtain epoxy phosphate; epoxy phosphate and acrylic acid are used for modifying epoxy resin, and an initiator is supplemented for secondary polymerization chain extension and cross-linking reaction, so that the obtained epoxy mixture has the curing film stability of an epoxy coating, the compact isolation effect of acrylic resin, the high adhesiveness of silicon resin to a metal surface and the phosphating treatment characteristic of phosphoric acid; and the paint has excellent water resistance, oil resistance, rust resistance and other corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of anticorrosive coatings and their production, and particularly to an inner-layer coating for anticorrosive and oil-resistant bellows and a preparation method thereof. Background Art

[0002] Industrial bellows are generally metal bellows. Due to the requirements of the use environment, the inner and outer layers of metal bellows generally need to be sprayed with coatings having various functions such as waterproof, oil-proof, scale-proof, and corrosion-proof. Metal bellows coatings generally include epoxy coatings, polyurethane coatings, acrylic coatings, inorganic coatings, perchloroethylene coatings, chlorinated rubber coatings, high chlorinated polyethylene coatings, and various other waterborne coatings.

[0003] Among them, the following three are relatively commonly used: 1) Epoxy coatings are based on epoxy resins, have good adhesion and chemical corrosion resistance, can form a strong protective film, effectively isolate the pipeline from the external environment, and prevent corrosion media from eroding; 2) Polyurethane coatings are based on polyurethane resins, can be cured at room temperature to form a tough coating, effectively resist the erosion of corrosion media such as acids, alkalis, solvents, and salt mists, and have good weather resistance and chemical corrosion resistance; 3) Acrylic coatings are based on acrylic resins, can form a dense coating, effectively isolate the contact of air, moisture, and corrosion media, play an anti-corrosion role, and have excellent weather resistance and chemical stability.

[0004] However, the inner layer of the metal bellows needs to be cleaned and rust-proof treated before spraying the anticorrosive coating. The phosphating layer formed by the rust-proof treatment forms an interfacial effect with the polymer in the casting film process, and due to the interaction between the functional groups in the organophosphorus compound and the film-forming polymer, small pores appear after the "on-site phosphating treatment", reducing the dry and wet adhesion between the coating film and the substrate, and even causing the flash corrosion problem of the waterborne coating film to the metal substrate. Therefore, the compatibility between the anticorrosive polymer paint film and the rust-proof treatment layer needs to be considered. Summary of the Invention

[0005] The purpose of the present invention is to solve the deficiencies existing in the prior art, and to propose an inner-layer coating for anticorrosive and oil-resistant bellows and a preparation method thereof.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solution:

[0007] An inner-layer coating for anticorrosive and oil-resistant bellows, comprising the following components in parts by weight:

[0008] 50 parts of acrylic acid-modified epoxy resin: that is, acrylic acid is polymerized to introduce an acrylic acid chain into the main chain of the epoxy resin;

[0009] 10 parts of epoxy phosphate ester: That is, the epoxy end groups of epoxy resin are subjected to ring-opening esterification reaction by phosphoric acid to generate epoxy phosphate ester with phosphate ester end groups, which has the ability to continue cross-linking reaction with the epoxy end groups of other chains;

[0010] 30 - 35 parts of additives: Film-forming aids, thickeners, surfactants, defoamers, titanium dioxide, zinc oxide, light calcium carbonate, bentonite are added step by step according to the weight ratio of 14 - 16:3 - 4:2 - 3:0.5 - 0.6:2:2:3:3;

[0011] Curing agent: The curing agent is added before use, and the molar dosage of the curing agent is 105% ± 2% of the epoxy equivalent of the system;

[0012] The balance is water: Adjust the solid content of the system to 30 - 40%.

[0013] The specific components and dosages of the additives are as follows:

[0014] Curing agent: Alkenyl succinic anhydride (ASA, Vertellus);

[0015] Film-forming aid: Polyethylene glycol, specifically PEG400;

[0016] Surfactant: Polyglycerol fatty acid ester;

[0017] Defoamer: Emulsified silicone oil defoamer;

[0018] Thickener: Carboxyethyl cellulose;

[0019] The particle sizes of titanium dioxide, zinc oxide, light calcium carbonate and bentonite are 200 - 300 mesh.

[0020] The present invention also provides a preparation method of an inner layer coating for an anti-corrosion and oil-resistant corrugated pipe, comprising the following steps:

[0021] 1) Synthesis of acrylic-modified epoxy resin:

[0022] Epoxy resin and a mixed solvent are mixed according to a weight ratio of 2:1, heated and stirred, the temperature is raised to 110 °C, the epoxy resin is completely dissolved, the mixed solution is added dropwise within 1 h, after the addition is completed, the temperature is raised to 115 ± 5 °C, and the reaction is kept for 2 h to obtain acrylic-modified epoxy resin;

[0023] 2) Synthesis of epoxy phosphate ester:

[0024] Epoxy resin and acetone are dissolved according to a weight ratio of 1:2, and a phosphoric acid acetone solution is added dropwise at room temperature, controlling the molar ratio of epoxy groups to phosphoric acid in the system to be 2:1. After the addition is completed, the mixture is stirred and reacted for 30 min until the acid value of the system remains unchanged and is in the range of 70 - 80 mgKOH / g to obtain epoxy phosphate ester with phosphate ester end groups;

[0025] 3) Epoxy mixing reaction:

[0026] Mix the epoxy phosphate ester and the newly prepared acrylic acid modified epoxy resin in a weight ratio of 1:5, add benzoyl peroxide (BPO) additionally, heat up to 115 ± 5 °C, stir and reflux for 1 h to remove free phosphoric acid and various vinyl monomers in the system, and detect that the acid value of the system < 50 mgKOH / g;

[0027] 4) Neutralization reaction:

[0028] Cool the system obtained in 3) to 50 °C, dropwise add distilled water to change the system from water-in-oil type to oil-in-water type, then add ammonia water for neutralization. After spinning off acetone under vacuum conditions at 40 °C with a rotary evaporator, continue to stir for 1 h and discharge. Control the solid content to be 35 ± 1%, and the epoxy mixture is obtained. The product is a white emulsion;

[0029] 5) Coating preparation:

[0030] Mix the epoxy mixture, film-forming aid, thickener, surfactant, defoamer, titanium dioxide, zinc oxide, light calcium carbonate, and bentonite in a weight ratio of 200:14 - 16:3 - 4:2 - 3:0.5 - 0.6:2:2:3:3, stir and mix at 50 °C (grind and mix with a colloid mill if appropriate), and continuously add water to adjust the system viscosity to 2000 - 3000 mPa·s and the solid content to be 30%;

[0031] Add a curing agent before use, stir evenly to obtain the finished coating, and perform coating (spraying or rolling), drying, and film forming.

[0032] The specific components and dosages of the reagents used in 1) are as follows:

[0033] Epoxy resin: Since the metal bellows need to adapt to the use modes of bending and folding, E22 epoxy resin (Shanghai Resin Factory) with a moderate epoxy value, small hardness, and good toughness is selected;

[0034] Monomer mixed solution: It is mixed by acrylic acid monomer, vinyl siloxane monomer, styrene, and benzoyl peroxide in a weight ratio of 100:20 - 30:40 - 45:2.5 - 3.5;

[0035] The acrylic acid monomer is a compound of n-butyl acrylate (n-BA) and methyl methacrylate (MMA) in a weight ratio of 1:0.5 - 0.6, both of industrial grade and produced by Beijing Orient Chemical Factory;

[0036] The vinyl siloxane monomer is vinyltriisopropoxysilane (C-1706) and vinyltriethoxysilane (A-151), both of analytical grade and produced by BYK Company;

[0037] Benzoyl peroxide (BPO), analytical pure, Tianjin Fuchen Chemical Reagent Factory;

[0038] Mixed solvent: Prepared by mixing propylene glycol methyl ether and n-butanol in a volume ratio of 2:1;

[0039] All other reagents are produced by Beijing Orient Chemical Plant.

[0040] The specific components and dosages of the reagents used in 2) are as follows:

[0041] Epoxy resin: Since this reaction is a ring-opening esterification reaction between epoxy groups and phosphoric acid, bisphenol A epoxy resin E44 (Shanghai Resin Factory) with a higher epoxy value and greater hardness is selected;

[0042] Phosphoric acid acetone solution: Prepared by mixing 85% concentrated phosphoric acid aqueous solution and acetone in a volume ratio of 1:3.

[0043] In 3), benzoyl peroxide accounts for 2% of the system weight.

[0044] After adding ammonia water for neutralization in 4), the pH value of the system is adjusted to 7.5 - 8.5.

[0045] After the coating finished product obtained in 5) is spray-coated inside the metal bellows, after shaping for 5 - 10 minutes, hot air at 60°C is introduced for ventilation for 10 minutes, and the paint film is shaped. Subsequently, hot air at 120°C is introduced for baking for 10 - 15 minutes, and a metal bellows with an anti-corrosion inner coating is obtained.

[0046] Compared with the prior art, the beneficial effects of the present invention are:

[0047] 1. By adding a copolymerized polymer side chain with acrylic acid, styrene, and vinyl siloxane to the side chain of the epoxy resin in the present invention, acrylic acid can improve water dispersibility, and siloxane can appropriately increase the crosslinking degree, both of which can improve the film-forming denseness, greatly reduce the film-forming water absorption rate, and thus improve the rust and corrosion prevention level; at the same time, acrylic acid can increase the drooling and spreading property of the coating film, and siloxane can improve the adhesion of the paint film to the metal substrate, thereby improving the film stability.

[0048] 2. By introducing phosphate end groups at the end of the epoxy resin in the present invention to obtain epoxy phosphate, on the one hand, similar to siloxane, phosphate can significantly improve the adhesion of the epoxy resin to the metal substrate and increase the crosslinking density of the paint film; on the other hand, phosphate undergoes a chemical reaction on the metal substrate to form a dense phosphating film, increasing the resistance to the corrosion reaction of the substrate metal and gradually enhancing the water resistance and anti-flash corrosion ability of the coating.

[0049] 3. The present invention mixes epoxy phosphate ester with newly prepared acrylic acid modified epoxy resin (polymerization not terminated), adds an initiator for secondary polymerization chain extension and cross-linking reaction, removes free phosphoric acid and various vinyl monomers in the system, and the obtained epoxy mixture has the solid film stability of epoxy anti-corrosion coatings, the dense isolation effect of acrylic anti-corrosion resin, the high adhesion of silicone resin to the metal surface, and the phosphating treatment characteristics of phosphoric acid for metal protection, thus having excellent anti-corrosion properties such as water resistance, oil resistance and rust prevention. Specific Embodiments

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0051] An anti-corrosion and oil-resistant inner layer coating for bellows, characterized by comprising the following components in parts by weight:

[0052] 50 parts of acrylic acid modified epoxy resin: that is, acrylic acid is polymerized to introduce an acrylic acid chain into the main chain of epoxy resin;

[0053] 10 parts of epoxy phosphate ester: that is, the epoxy end group of epoxy resin is subjected to ring-opening esterification reaction with phosphoric acid to generate epoxy phosphate ester with a phosphate ester end group, which has the ability to continue cross-linking reaction with the epoxy end groups of other chains;

[0054] 30 - 35 parts of additives: film-forming aids, thickeners, surfactants, defoamers, titanium dioxide, zinc oxide, light calcium carbonate, bentonite are added step by step according to a weight ratio of 14 - 16:3 - 4:2 - 3:0.5 - 0.6:2:2:3:3;

[0055] Curing agent: The curing agent is added before use, and the molar dosage of the curing agent is 105% ± 2% of the epoxy equivalent of the system;

[0056] The balance is water: adjust the solid content of the system to 30 - 40%.

[0057] Preparation Example A1:

[0058] Synthesis of acrylic acid modified epoxy resin:

[0059] Epoxy resin and a mixed solvent are mixed according to a weight ratio of 2:1, heated and stirred, the temperature is raised to 110°C, the epoxy resin is completely dissolved, the mixed solution is added dropwise within 1 h, and after the addition is completed, the temperature is raised to 115 ± 5°C and kept for reaction for 2 h to obtain acrylic acid modified epoxy resin;

[0060] Epoxy resin: Since the metal bellows need to adapt to the use modes of bending and folding, E22 epoxy resin (Shanghai Resin Factory) with a moderate epoxy value, small hardness and good toughness is selected.

[0061] Monomer mixed solution: It is prepared by mixing acrylic monomers, vinyl siloxane monomers, styrene and benzoyl peroxide in a weight ratio of 100:20:45:3.5;

[0062] The acrylic monomers are a compound of n-butyl acrylate (n-BA) and methyl methacrylate (MMA) in a weight ratio of 1:0.6, both of industrial grade and produced by Beijing Orient Chemical Factory;

[0063] The vinyl siloxane monomers are vinyltriisopropoxysilane (C-1706) and vinyltriethoxysilane (A-151), both of analytical purity and produced by BYK Company;

[0064] Benzoyl peroxide (BPO), of analytical purity, produced by Tianjin Fuchen Chemical Reagent Factory;

[0065] Mixed solvent: It is prepared by mixing propylene glycol monomethyl ether and n-butanol in a volume ratio of 2:1;

[0066] The rest of the reagents are all produced by Beijing Orient Chemical Factory.

[0067] Preparation Example A2:

[0068] Synthesis of acrylic acid modified epoxy resin:

[0069] Epoxy resin and the mixed solvent are mixed in a weight ratio of 2:1, heated and stirred, and the temperature is raised to 110 °C until the epoxy resin is completely dissolved. The mixed solution is added dropwise within 1 h. After the addition is completed, the temperature is raised to 115 ± 5 °C and kept for reaction for 2 h to obtain acrylic acid modified epoxy resin;

[0070] Epoxy resin: Since the metal bellows need to adapt to the use modes of bending and folding, E22 epoxy resin (Shanghai Resin Factory) with a moderate epoxy value, relatively low hardness and good toughness is selected;

[0071] Monomer mixed solution: It is prepared by mixing acrylic monomers, vinyl siloxane monomers, styrene and benzoyl peroxide in a weight ratio of 100:25:42:3;

[0072] The acrylic monomers are a compound of n-butyl acrylate (n-BA) and methyl methacrylate (MMA) in a weight ratio of 1:0.5, both of industrial grade and produced by Beijing Orient Chemical Factory;

[0073] The vinyl siloxane monomers are vinyltriisopropoxysilane (C-1706) and vinyltriethoxysilane (A-151), both of analytical purity and produced by BYK Company;

[0074] Benzoyl peroxide (BPO), of analytical purity, produced by Tianjin Fuchen Chemical Reagent Factory;

[0075] Mixed solvent: Propylene glycol methyl ether and n-butanol are compounded according to a volume ratio of 2:1;

[0076] All other reagents are produced by Beijing Orient Chemical Plant.

[0077] Preparation Example A3:

[0078] Synthesis of acrylic acid modified epoxy resin:

[0079] The epoxy resin and the mixed solvent are mixed according to a weight ratio of 2:1, heated and stirred, and the temperature is raised to 110 °C until the epoxy resin is completely dissolved. The mixed solution is added dropwise within 1 h. After the addition is completed, the temperature is raised to 115 ± 5 °C and kept warm for reaction for 2 h to obtain acrylic acid modified epoxy resin;

[0080] Epoxy resin: Since the metal bellows need to adapt to the use modes of bending and folding, E22 epoxy resin (Shanghai Resin Factory) with a moderate epoxy value, small hardness and good toughness is selected.

[0081] Monomer mixed solution: Acrylic acid monomer, vinyl siloxane monomer, styrene and benzoyl peroxide are mixed according to a weight ratio of 100:30:40:2.5;

[0082] The acrylic acid monomer is compounded from n-butyl acrylate (n-BA) and methyl methacrylate (MMA) according to a weight ratio of 1:0.55, both of which are industrial grade and produced by Beijing Orient Chemical Plant;

[0083] The vinyl siloxane monomer is vinyltriisopropoxysilane (C-1706) and vinyltriethoxysilane (A-151), both of which are of analytical purity and produced by BYK Company;

[0084] Benzoyl peroxide (BPO), analytical purity, Tianjin Fuchen Chemical Reagent Factory;

[0085] Mixed solvent: Propylene glycol methyl ether and n-butanol are compounded according to a volume ratio of 2:1;

[0086] All other reagents are produced by Beijing Orient Chemical Plant.

[0087] Preparation Example B1:

[0088] Synthesis of epoxy phosphate:

[0089] The epoxy resin and acetone are dissolved according to a weight ratio of 1:2, and the phosphoric acid acetone solution is added dropwise at room temperature, controlling the molar ratio of epoxy groups to phosphoric acid in the system to be 2:1. After the addition is completed, stir and react for 30 min until the acid value of the system remains unchanged and is between 70 - 80 mgKOH / g to obtain epoxy phosphate with phosphate ester end groups;

[0090] Epoxy resin: This reaction is a ring-opening esterification reaction between epoxy groups and phosphoric acid. Therefore, bisphenol A epoxy resin E44 (Shanghai Resin Factory) with a higher epoxy value and greater hardness is selected.

[0091] Phosphoric acid acetone solution: It is prepared by mixing an 85% by weight concentrated phosphoric acid aqueous solution and acetone in a volume ratio of 1:3.

[0092] Example 1:

[0093] A preparation method of an inner layer coating for anti-corrosion and oil-resistant bellows, comprising the following steps:

[0094] 1) Epoxy mixing reaction:

[0095] Mix the epoxy phosphate obtained in Preparation Example B1 and the newly prepared acrylic acid-modified epoxy resin in Preparation Example A1 in a weight ratio of 1:5, and add benzoyl peroxide (BPO). Benzoyl peroxide accounts for 2% of the system weight. Heat up to 115 ± 5 °C and stir and reflux for 1 h to remove free phosphoric acid and various vinyl monomers in the system. Detect that the acid value of the system is < 50 mgKOH / g.

[0096] 2) Neutralization reaction:

[0097] Cool the system obtained in 1) to 50 °C, dropwise add distilled water to change the system from a water-in-oil type to an oil-in-water type, then add ammonia water for neutralization, adjust the pH value of the system to 7.5 - 8.5, spin off acetone under vacuum conditions at 40 °C with a rotary evaporator, and continue stirring for 1 h to discharge. Control the solid content to be 35 ± 1%, and an epoxy mixture is obtained. The product is a white emulsion.

[0098] 3) Coating preparation:

[0099] Mix the epoxy mixture, film-forming aid, thickener, surfactant, defoamer, titanium dioxide, zinc oxide, light calcium carbonate, and bentonite in a weight ratio of 200:14:4:3:0.5:2:2:3:3, stir and mix at 50 °C (grinding and mixing can be carried out with a colloid mill when appropriate), and continuously add water to adjust the system viscosity to 2000 - 3000 mPa·s and the solid content to 30%.

[0100] The specific components and dosages of the said additives are as follows:

[0101] Curing agent: alkenyl succinic anhydride (ASA, Vertellus);

[0102] Film-forming aid: polyethylene glycol, specifically PEG400;

[0103] Surfactant: polyglycerol fatty acid ester;

[0104] Defoamer: emulsified silicone oil defoamer;

[0105] Thickener: Carboxyethyl cellulose;

[0106] The particle sizes of titanium dioxide, zinc oxide, light calcium carbonate, and bentonite are 200 - 300 mesh.

[0107] Before use, add a curing agent and stir evenly to obtain the finished coating; after the obtained finished coating is spray-coated inside the metal bellows, shape it for 5 - 10 minutes, then pass in hot air at 60°C for ventilation for 10 minutes, and shape the paint film. Subsequently, pass in hot air at 120°C and bake for 10 - 15 minutes to obtain a metal bellows with an anti-corrosion inner coating.

[0108] Example 2:

[0109] A preparation method for the inner layer coating of an anti-corrosion and oil-resistant bellows, comprising the following steps:

[0110] 1) Epoxy mixing reaction:

[0111] Mix the epoxy phosphate obtained in Preparation Example B1 and the newly prepared acrylic acid-modified epoxy resin in Preparation Example A2 according to a weight ratio of 1:5, and add benzoyl peroxide (BPO). Benzoyl peroxide accounts for 2% of the system weight. Heat up to 115 ± 5°C and stir and reflux for 1 hour to remove free phosphoric acid and various vinyl monomers in the system. Detect that the acid value of the system < 50 mgKOH / g;

[0112] 2) Neutralization reaction:

[0113] Cool the system obtained in 1) to 50°C, dropwise add distilled water to change the system from a water-in-oil type to an oil-in-water type, then add ammonia water for neutralization, adjust the pH value of the system to 7.5 - 8.5, use a rotary evaporator to spin off acetone under vacuum at 40°C, and continue to stir for 1 hour and discharge. Control the solid content to be 35 ± 1% to obtain an epoxy mixture. The product is a white emulsion;

[0114] 3) Coating preparation:

[0115] Mix the epoxy mixture, film-forming aid, thickener, surfactant, defoamer, titanium dioxide, zinc oxide, light calcium carbonate, and bentonite according to a weight ratio of 200:16:3:3:0.6:2:2:3:3, stir and mix at 50°C (grind and mix with a colloid mill when appropriate), and continuously add water to adjust the system viscosity to 2000 - 3000 mPa·s and the solid content to 30%;

[0116] The specific components and dosages of the additives are as follows:

[0117] Curing agent: Alkenyl succinic anhydride (ASA, Vertellus);

[0118] Film-forming aid: Polyethylene glycol, specifically PEG400;

[0119] Surfactant: polyglycerol fatty acid ester;

[0120] Defoamer: emulsified silicone oil defoamer;

[0121] Thickener: carboxyethyl cellulose;

[0122] The particle sizes of titanium dioxide, zinc oxide, light calcium carbonate and bentonite are 200 - 300 mesh.

[0123] Before use, add a curing agent and stir evenly to obtain the finished coating; after the obtained finished coating is spray-coated inside the metal bellows, after shaping for 5 - 10 min, pass in hot air at 60 °C for ventilation for 10 min, and shape the paint film, and then pass in hot air at 120 °C for baking for 10 - 15 min to obtain a metal bellows with an anti-corrosion inner coating.

[0124] Example 3:

[0125] A preparation method of an anti-corrosion and oil-resistant bellows inner layer coating, comprising the following steps:

[0126] 1) Epoxy mixing reaction:

[0127] Mix the epoxy phosphate obtained in Preparation Example B1 and the newly prepared acrylic acid-modified epoxy resin in Preparation Example A3 according to a weight ratio of 1:5, and add benzoyl peroxide (BPO), and benzoyl peroxide accounts for 2% of the system weight. Heat up to 115 ± 5 °C and stir and reflux for 1 h to remove free phosphoric acid and various vinyl monomers in the system, and detect that the acid value of the system < 50 mgKOH / g;

[0128] 2) Neutralization reaction:

[0129] Cool the system obtained in 1) to 50 °C, dropwise add distilled water to change the system from water-in-oil type to oil-in-water type, then add ammonia water for neutralization, adjust the pH value of the system to 7.5 - 8.5, and use a rotary evaporator to spin off acetone under vacuum at 40 °C, and then continue to stir for 1 h to discharge, and control the solid content to be 35 ± 1% to obtain an epoxy mixture, and the product is a white emulsion;

[0130] 3) Coating preparation:

[0131] Mix the epoxy mixture, film-forming aid, thickener, surfactant, defoamer, titanium dioxide, zinc oxide, light calcium carbonate, and bentonite according to a weight ratio of 200:15:3.5:2.5:0.55:2:2:3:3, stir and mix at 50 °C (grinding and mixing can be carried out with a colloid mill when appropriate), and continuously add water to adjust the system viscosity to 2000 - 3000 mPa·s and the solid content to be 30%;

[0132] The specific components and dosages of the said additives are as follows:

[0133] Curing agent: Vinyl succinic anhydride (ASA, Vantruex);

[0134] Film-forming auxiliary agent: Polyethylene glycol, specifically PEG400;

[0135] Surfactant: Polyglycerol fatty acid ester;

[0136] Defoaming agent: Emulsified silicone oil defoaming agent;

[0137] Thickening agent: Carboxyethyl cellulose;

[0138] The particle sizes of titanium dioxide, zinc oxide, light calcium carbonate and bentonite are 200 - 300 mesh.

[0139] Add the curing agent before use, stir evenly to obtain the finished coating; after spraying and coating the obtained finished coating inside the metal bellows, shape it for 5 - 10 min, then introduce hot air at 60 °C for ventilation for 10 min, and shape the paint film, and then introduce hot air at 120 °C to bake for 10 - 15 min to obtain a metal bellows with an anti-corrosion inner coating.

[0140] Comparative Example 1:

[0141] A preparation method of an anti-corrosion and oil-resistant bellows inner layer coating includes the following steps:

[0142] 1) Neutralization reaction:

[0143] Place the acrylic acid-modified epoxy resin obtained in Preparation Example A3 in air for 24 h, mix it with the epoxy phosphate ester obtained in Preparation Example B1 according to a weight ratio of 5:1, cool the obtained system to 50 °C, dropwise add distilled water to change the system from a water-in-oil type to an oil-in-water type, then add ammonia water for neutralization, adjust the pH value of the system to 7.5 - 8.5, spin off acetone under vacuum at 40 °C with a rotary evaporator, and then continue stirring for 1 h to discharge, controlling the solid content to be 35 ± 1%, to obtain an epoxy mixture, and the product is a white emulsion;

[0144] 2) Coating preparation:

[0145] Mix the epoxy mixture, film-forming auxiliary agent, thickening agent, surfactant, defoaming agent, titanium dioxide, zinc oxide, light calcium carbonate, and bentonite according to a weight ratio of 200:15:3.5:2.5:0.55:2:2:3:3, stir and mix at 50 °C (grind and mix with a colloid mill when appropriate), and continuously add water to adjust the system viscosity to 2000 - 3000 mPa·s and the solid content to 30%;

[0146] The specific components and dosages of the auxiliary agents are as follows:

[0147] Curing agent: Vinyl succinic anhydride (ASA, Vantruex);

[0148] Film-forming aid: polyethylene glycol, specifically PEG400;

[0149] Surfactant: polyglycerol fatty acid ester;

[0150] Defoamer: emulsified silicone oil defoamer;

[0151] Thickener: carboxyethyl cellulose;

[0152] The particle sizes of titanium dioxide, zinc oxide, light calcium carbonate and bentonite are 200 - 300 mesh.

[0153] Before use, add a curing agent and stir evenly to obtain the finished coating; after spraying and coating the obtained finished coating inside the metal bellows, set for 5 - 10 min, then pass through hot air at 60 °C for ventilation for 10 min and shape the paint film, and then pass through hot air at 120 °C for baking for 10 - 15 min to obtain a metal bellows with an anti-corrosion inner coating.

[0154] Comparative Example 2:

[0155] A preparation method of an anti-corrosion and oil-resistant bellows inner layer coating, comprising the following steps:

[0156] 1) Epoxy mixing reaction:

[0157] Mix the epoxy phosphate obtained in Preparation Example B1 and the newly prepared acrylic-modified epoxy resin in Preparation Example A3 according to a weight ratio of 1:5, and add benzoyl peroxide (BPO). Benzoyl peroxide accounts for 2% of the system weight. Heat up to 115 ± 5 °C and stir and reflux for 1 h to remove free phosphoric acid and various vinyl monomers in the system. Detect that the acid value of the system < 50 mgKOH / g;

[0158] 2) Neutralization reaction:

[0159] After spinning off acetone from the system obtained in 1) under vacuum at 40 °C, continue to stir for 1 h and discharge. Control the solid content to be 35 ± 1% to obtain an epoxy mixture. The product is a white emulsion;

[0160] 3) Coating preparation:

[0161] Mix the epoxy mixture, film-forming aid, thickener, surfactant, defoamer, titanium dioxide, zinc oxide, light calcium carbonate, and bentonite according to a weight ratio of 200:15:3.5:2.5:0.55:2:2:3:3, stir and mix at 50 °C, and continuously add water to adjust the system viscosity to 2000 - 3000 mPa·s and the solid content to 30%;

[0162] The specific components and dosages of the auxiliaries are as follows:

[0163] Curing agent: alkenyl succinic anhydride (ASA, Vantrus);

[0164] Film-forming aid: polyethylene glycol, specifically PEG400;

[0165] Surfactant: polyglycerol fatty acid ester;

[0166] Defoaming agent: emulsified silicone oil defoaming agent;

[0167] Thickening agent: carboxyethyl cellulose;

[0168] The particle sizes of titanium dioxide, zinc oxide, light calcium carbonate and bentonite are 200 - 300 mesh.

[0169] Add the curing agent before use, stir evenly to obtain the finished coating; after spraying and coating the obtained finished coating inside the metal bellows, set for 5 - 10 min, then pass in hot air at 60 °C for ventilation for 10 min and shape the paint film, and then pass in hot air at 120 °C for baking for 10 - 15 min to obtain a metal bellows with an anti-corrosion inner coating.

[0170] Comparative Example 3:

[0171] A preparation method of an anti-corrosion and oil-resistant bellows inner layer coating, comprising the following steps:

[0172] 1) Epoxy mixing reaction:

[0173] Mix bisphenol A epoxy resin E44 and the newly prepared acrylic-modified epoxy resin in Preparation Example A3 in a weight ratio of 1:5, and add benzoyl peroxide (BPO) additionally. Benzoyl peroxide accounts for 2% of the system weight. Heat up to 115 ± 5 °C, stir and reflux for 1 h to remove free phosphoric acid and various vinyl monomers in the system, and detect that the acid value of the system < 50 mgKOH / g;

[0174] 2) Neutralization reaction:

[0175] Cool the system obtained in 1) to 50 °C, dropwise add distilled water to change the system from oil-in-water type to water-in-oil type, then add ammonia water for neutralization, adjust the pH value of the system to 7.5 - 8.5, continue stirring for 1 h and discharge, and control the solid content to be 35 ± 1% to obtain an epoxy mixture. The product is a white emulsion;

[0176] 3) Coating preparation:

[0177] Mix epoxy mixture, film-forming aid, thickener, surfactant, defoamer, titanium dioxide, zinc oxide, light calcium carbonate, and bentonite according to a weight ratio of 200:15:3.5:2.5:0.55:2:2:3:3, stir and mix at 50 °C (grind and mix with a colloid mill when appropriate), and continuously add water to adjust the system viscosity to 2000 - 3000 mPa·s and the solid content to 30%;

[0178] The specific components and dosages of the additives are as follows:

[0179] Curing agent: alkenyl succinic anhydride (ASA, Vantrue);

[0180] Film-forming aid: polyethylene glycol, specifically PEG400;

[0181] Surfactant: polyglycerol fatty acid ester;

[0182] Defoamer: emulsified silicone oil defoamer;

[0183] Thickener: carboxyethyl cellulose;

[0184] The particle sizes of titanium dioxide, zinc oxide, light calcium carbonate, and bentonite are 200 - 300 mesh.

[0185] Add the curing agent before use, stir evenly to obtain the finished coating; after spraying and coating the obtained finished coating inside the metal bellows, shape it for 5 - 10 min, then pass 60 °C hot air for ventilation for 10 min and shape the paint film, and then pass 120 °C hot air for baking for 10 - 15 min to obtain a metal bellows with an anti-corrosion inner coating

[0186] Comparative Example 4:

[0187] A preparation method of an anti-corrosion and oil-resistant bellows inner layer coating, comprising the following steps:

[0188] 1) Neutralization reaction:

[0189] Mix the epoxy phosphate ester obtained in Preparation Example B1 and epoxy resin E22 according to a weight ratio of 1:5, cool the obtained mixture to 50 °C, dropwise add distilled water to change the system from water-in-oil type to oil-in-water type, then add ammonia water for neutralization, adjust the system pH value to 7.5 - 8.5, spin off acetone with a rotary evaporator under vacuum conditions at 40 °C, and continue stirring for 1 h to discharge, controlling the solid content to be 35 ± 1%, thus obtaining the epoxy mixture, and the product is a white emulsion;

[0190] 2) Coating preparation:

[0191] Mix epoxy mixture, film-forming aid, thickener, surfactant, defoamer, titanium dioxide, zinc oxide, light calcium carbonate, and bentonite in a weight ratio of 200:15:3.5:2.5:0.55:2:2:3:3, stir and mix at 50 °C (grind and mix with a colloid mill when appropriate), and continuously add water to adjust the system viscosity to 2000 - 3000 mPa·s and the solid content to 30%;

[0192] The specific components and dosages of the above-mentioned aids are as follows:

[0193] Curing agent: alkenyl succinic anhydride (ASA, Vertellus);

[0194] Film-forming aid: polyethylene glycol, specifically PEG400;

[0195] Surfactant: polyglycerol fatty acid ester;

[0196] Defoamer: emulsified silicone oil defoamer;

[0197] Thickener: carboxyethyl cellulose;

[0198] The particle sizes of titanium dioxide, zinc oxide, light calcium carbonate, and bentonite are 200 - 300 mesh.

[0199] Add the curing agent before use, stir evenly to obtain the finished coating; after spraying and coating the finished coating inside the metal bellows, shape it for 5 - 10 min, then pass in hot air at 60 °C for ventilation for 10 min, and shape the paint film, and then pass in hot air at 120 °C for baking for 10 - 15 min to obtain a metal bellows with an anti-corrosion inner coating.

[0200] Performance test:

[0201] 1. Film-forming performance:

[0202] Spray Examples 1 - 3 and Comparative Examples 1 - 4 to a thickness of 20 μm, and observe whether there are cracks in each paint film after 30 days. The specific results are shown in Table 1 below:

[0203] Table 1. Film-forming performance of the epoxy coating finished product

[0204]

[0205] It shows that acrylic-modified epoxy resin is crucial for film formation; epoxy phosphate has an auxiliary effect on the stability of the film structure; and the neutralization reaction is to adjust salt formation, improve water solubility and water dispersibility, thus affecting film-forming uniformity; whether there is chain extension and cross-linking of the epoxy mixing reaction has no effect on film formation itself and the stability of the paint film.

[0206] 2. Paint film hardness:

[0207] The hardness was measured with reference to the national standard GB / T 6739-1996 "Determination of Film Hardness by Pencil Test", and the hardness of the cured film of the waterborne epoxy phosphate emulsion was measured by the manual method. The hardness levels are 9H, 8H, 7H, 6H, 5H, 4H, 3H, 2H, H, F, HB, B, 2B, 3B, 4B, 5B, 6B, a total of 16 levels, with 9H being the hardest and 6B being the softest.

[0208] 3. Adhesion of paint film:

[0209] For the determination of adhesion, a relatively complete area was selected on the cured paint film, and a uniform small square grid was scratched on the coating surface with a single-blade knife using the cross-cut method. Then, 3M600 tape from Shenzhen Fanya Adhesive Products Co., Ltd. was used for testing, and the experimental grade was recorded. The adhesion decreased in turn from 0 to 5 -

[0210] Grade 0: The cutting edges are completely smooth and none of the grids peel off;

[0211] Grade 1: There is a little coating peeling at the intersection of the cuts, but the affected cross-cut area is not significantly greater than 5%;

[0212] Grade 2: There is coating peeling at the intersection of the cuts and / or along the cutting edges, and the affected cross-cut area is significantly greater than 5%, but not significantly greater than 15%;

[0213] Grade 3: The coating partially or completely peels off in large pieces along the cutting edges, and / or partially or completely flakes off at different parts of the grid. The affected cross-cut area is significantly greater than 15%, but not significantly greater than 35%;

[0214] Grade 4: The coating peels off in large pieces along the cutting edges, and / or some squares partially or completely peel off. The affected cross-cut area is significantly greater than 35%, but not significantly greater than 65%;

[0215] Grade 5: The degree of peeling exceeds grade 4.

[0216] 4. Boiling water resistance:

[0217] The cured film was completely immersed in water at 95°C. After standing for 1 h, the specimen was taken out, and after it cooled naturally, it was left standing at room temperature for 1 h. The above is one boiling water cycle; each specimen was subjected to two cycles; finally, the specimen was taken out, and the changes in the bonding situation between the film and the substrate and the effects on the hardness, adhesion, and appearance of the paint film were observed, and whether the paint film bubbled and peeled was visually inspected.

[0218] 5. Oil resistance:

[0219] Refer to standard HGT 3343-85 "Determination of oil resistance of paint film". After the paint film is completely dry, immerse 2 / 3 of the area of ​​the painted test panel in gasoline at a temperature of 25±1°C. After the immersion time specified in the product standard is reached, take out the test panel and dry it with filter paper. Under constant temperature and humidity conditions, check the paint film surface for wrinkling, blistering, peeling, softening, discoloration, loss of gloss, etc. The qualification shall be determined in accordance with the product standard.

[0220] 6. Flexibility:

[0221] The ability of a paint film to deform with its substrate without being damaged. To meet the needs of different deformations (impact, vibration, heat and cold, expansion and contraction). The national standard stipulates that the test method for paint film flexibility is: the minimum shaft rod diameter on the flexibility tester that does not cause the paint film to bend or break is used. The flexibility of paint with good flexibility is generally 1 to 3 mm.

[0222] Test method: Prepare the paint film on the tinplate (or as specified in the product standard) according to CB1727-79 "General Preparation Method for Paint Film". After the paint film is completely dry, press the painted sample with both hands on a shaft rod with a diameter specified in the product standard with the paint film facing upward under constant temperature and humidity conditions, and bend it around the rod. After bending, the thumbs of both hands should be symmetrical to the center line of the shaft rod. The bending action must be completed within 2 to 3 seconds. Observe the paint film with a 4x magnifying glass after bending. If there are damage phenomena such as reticulation, cracks and peeling, it is unqualified.

[0223] 7. Anti-rust function:

[0224] Polarization curve and AC impedance (EIS) test adopts Shanghai Chenhua CHI660E electrochemical workstation system, with 1.5cm×1cm platinum sheet as counter electrode, coating / carbon steel electrode as working electrode, saturated calomel electrode with Luggin capillary as reference electrode, and 3.5% NaCl solution as test medium. The change value of coating resistance (R) after immersion in 3.5% NaCl solution for 24h is tested, and the change value / original coating resistance value is taken as the anti-rust index θ, and θ<5% is a qualified product.

[0225] The performance test is shown in Table 2 below:

[0226] Table 2. Performance test of epoxy coating finished film

[0227]

[0228]

[0229] 1) As can be seen from Table 2, the factors affecting hardness are many and complex, but acrylic modified epoxy resin is more flexible, which is conducive to reducing hardness and flexibility to adapt to the use of corrugated bending and wrinkling;

[0230] 2) Organosiloxane and epoxy phosphate have an important impact on the adhesion of the paint film. The epoxy mixing reaction and neutralization reaction affect the adhesion by influencing the water dispersibility of the paint solution and the uniformity of the paint film.

[0231] 3) Acrylic modified epoxy resin has a decisive influence on the water boiling resistance and oil resistance of the paint film through film densification. The epoxy mixing reaction and neutralization reaction play an important auxiliary role in the water boiling resistance and oil resistance of the paint film.

[0232] 4) Epoxy phosphate has a decisive influence on the rust prevention function. Acrylic modified epoxy resin affects the stability of the film against electrochemical corrosion through film densification. The remaining epoxy mixing reaction and neutralization reaction affect the electrochemical corrosiveness (i.e., rust prevention function) by influencing the water dispersibility of the paint solution and the uniformity of the paint film.

[0233] The following conclusions are drawn:

[0234] 1) By adding copolymerized polymer side chains with acrylic acid, styrene, and vinyl siloxane to the side chains of epoxy resin, acrylic acid can improve water dispersibility, and siloxane can appropriately increase the crosslinking degree, both of which can improve film densification, greatly reduce the water absorption rate of the film, and thus improve the rust prevention and anti-corrosion level. At the same time, acrylic acid can increase the spreading property of the coating film, and siloxane can improve the adhesion of the paint film to the metal substrate, thereby improving the stability of the paint film.

[0235] 2) By introducing phosphate end groups at the end of epoxy resin to obtain epoxy phosphate, on the one hand, similar to siloxane, phosphate can significantly improve the adhesion of epoxy resin to the metal substrate and increase the crosslinking density of the paint film. On the other hand, phosphate undergoes a chemical reaction on the metal substrate to form a dense phosphating film, increasing the resistance to the corrosion reaction of the substrate metal and gradually enhancing the water resistance and anti-flash corrosion ability of the coating.

[0236] 3) By mixing epoxy phosphate and newly prepared acrylic modified epoxy resin (polymerization not terminated), adding an initiator for secondary polymerization chain extension and crosslinking reaction, and removing free phosphoric acid and various vinyl monomers in the system, the obtained epoxy mixture has the stability of the cured film of epoxy anti-corrosion coating, the dense isolation effect of acrylic anti-corrosion resin, the high adhesion of organosilicon resin to the metal surface, and the phosphating treatment characteristics of phosphoric acid for metal protection, thus having excellent anti-corrosion properties such as water resistance, oil resistance, and rust prevention.

[0237] As mentioned above, it is only the preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered within the protection scope of the present invention.

Claims

1. An anti-corrosion and oil-resistant bellows inner coating, characterized in that: The composition comprises the following components in parts by weight: 50 parts of acrylic acid modified epoxy resin; 10 parts of epoxy phosphate; 30-35 parts of additives: film-forming aid, thickener, surfactant, defoamer, titanium dioxide, zinc oxide, light calcium carbonate, bentonite are added in steps according to the weight ratio of 14-16:3-4:2-3:0.5-0.6:2:2:3:3; Curing agent: Add curing agent before use, the molar amount of curing agent is 105% ± 2% of the epoxy equivalent of the system; The rest is water: adjust the solid content of the system to 30-45%.

2. The anti-corrosion and oil-resistant inner layer coating for a corrugated pipe according to claim 1 is characterized in that: The specific ingredients and dosage of the auxiliary agent are as follows: Curing agent: alkenyl succinic anhydride; Film-forming aid: polyethylene glycol, specifically PEG400; Surfactant: polyglycerol fatty acid ester; Defoaming agent: emulsified silicone oil defoaming agent; Thickener: carboxyethyl cellulose; The particle sizes of titanium dioxide, zinc oxide, light calcium carbonate and bentonite are 200-300 meshes.

3. The method for preparing the anti-corrosion and oil-resistant inner layer coating of a corrugated pipe according to claim 1, characterized in that: The following steps are involved: 1) Synthesis of acrylic acid modified epoxy resin: The epoxy resin and the mixed solvent were mixed in a weight ratio of 2:1, heated and stirred, and the temperature was raised to 110°C. The epoxy resin was completely dissolved, and the mixed solution was added dropwise within 1 hour. After the addition was completed, the temperature was raised to 115±5°C and kept warm for 2 hours to obtain an acrylic acid-modified epoxy resin; 2) Synthesis of epoxy phosphate: The epoxy resin and acetone were dissolved in a weight ratio of 1:2, and the acetone phosphate solution was added dropwise at room temperature to control the molar ratio of epoxy group to phosphoric acid in the system to be 2:

1. After the addition was completed, the mixture was stirred and reacted for 30 minutes until the acid value of the system remained unchanged and was between 70 and 80 mgKOH / g, thereby obtaining an epoxy phosphate ester with a phosphate end group; 3) Epoxy mixing reaction: Epoxy phosphate and newly prepared acrylic modified epoxy resin were mixed in a weight ratio of 1:5, and dibenzoyl peroxide was added, and the temperature was raised to 115±5°C, and stirred and refluxed for 1 hour to remove free phosphoric acid and various vinyl monomers in the system. The acid value of the system was detected to be less than 50 mgKOH / g; 4) Neutralization reaction: The system obtained in 3) was cooled to 50°C, and distilled water was added dropwise to change the system from water-in-oil type to oil-in-water type, and then ammonia was added for neutralization. After the acetone was removed by rotary evaporation at 40°C under vacuum conditions, stirring was continued for 1 hour, and the solid content was controlled to be 35±1%, and the epoxy mixture was obtained. The product was a white emulsion; 5) Coating preparation: The epoxy mixture, film-forming aid, thickener, surfactant, defoamer, titanium dioxide, zinc oxide, light calcium carbonate and bentonite are stirred and mixed at 50° C. in a weight ratio of 200:14-16:3-4:2-3:0.5-0.6:2:2:3:3, and water is continuously added to adjust the system viscosity to 2000-3000 mPa·s and the solid content to 30%; Add curing agent before use and stir evenly to obtain the finished coating product, which can then be applied, dried and film-formed.

4. The method for preparing the anti-corrosion and oil-resistant inner layer coating of a corrugated pipe according to claim 3, characterized in that: The specific components and dosages of the reagents used in 1) are as follows: Epoxy resin: E22 epoxy resin; Monomer mixed solution: acrylic acid monomer, vinyl siloxane monomer, styrene and dibenzoyl peroxide are mixed in a weight ratio of 100:20-30:40-45:2.5-3.5; The acrylic acid monomer is prepared by mixing n-butyl acrylate and methyl methacrylate in a weight ratio of 1:0.5-0.6; The vinyl siloxane monomers are vinyl triisopropoxysilane and vinyl triethoxysilane; Mixed solvent: Propylene glycol methyl ether and n-butanol are compounded in a volume ratio of 2:

1.

5. The method for preparing the anti-corrosion and oil-resistant inner coating of a corrugated pipe according to claim 3, characterized in that: The specific components and dosages of the reagents used in 2) are as follows: Epoxy resin: bisphenol A epoxy resin E44; Phosphate-acetone solution: A mixture of 85% by weight concentrated phosphoric acid aqueous solution and acetone in a volume ratio of 1:

3.

6. The method for preparing an anti-corrosion and oil-resistant bellows inner coating according to claim 3, characterized in that: In the above 3), the dibenzoyl peroxide accounts for 2% of the system weight.

7. The method for preparing an anti-corrosion and oil-resistant inner layer coating for a corrugated pipe according to claim 3, characterized in that: After neutralization by adding ammonia water in the step 4), the pH value of the system is adjusted to 7.5-8.

5.

8. The method for preparing an anti-corrosion and oil-resistant inner layer coating for a corrugated pipe according to claim 3, characterized in that: After the finished coating product obtained in 5) is sprayed on the inside of the metal bellows and shaped for 5-10 minutes, 60°C hot air is introduced for ventilation for 10 minutes to shape the paint film, and then 120°C hot air is introduced for baking for 10-15 minutes to obtain a metal bellows with an anti-corrosion inner coating.

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